JPH0537519Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a shielding device for a power supply circuit, and particularly to a magnetic shielding device suitable for use in a magnetic flux control type switching power supply circuit, etc.

[Summary of the idea]

The present invention relates to a shielding device for a power supply circuit, which has a simple structure by sandwiching the power supply circuit between two heat sinks on a circuit board and surrounding it from above and below with a pair of U-shaped shield cases. The leakage magnetic flux of the power supply circuit section is shielded to prevent heat from accumulating inside the shield case.

[Conventional technology]

As a conventional shielding device for a power supply circuit, for example, one shown in FIG. 3 is known.

The shield device 30 shown in FIG. 3 is for shielding a magnetic flux control type switching power supply device such as that disclosed in Japanese Patent Application Laid-Open No. 62-64266, for example. A heat sink 35 with a power transistor 34 attached thereto is installed on a circuit board 33 on which a PRT (power regulation transformer) 31, a PIT (power isolation transformer) 32, etc. are installed, and an input lead wire 36, an output lead wire It was composed of 37.

PIT3 of the above magnetic flux control type switching power supply circuit
2 is operated by leakage inductance,
Structurally, the primary winding and the secondary winding are wound with an insulating distance between them, which is the middle of the bobbin, so that a large amount of leakage magnetic flux is generated.

In order to shield this leakage magnetic flux, the entire power supply circuit is covered with a shield case 38, and the front and rear openings of the shield case 38 are covered with cover plates 39a and 39b.
It had a so-called completely sealed structure.

[The problem that the idea aims to solve]

However, in the shield device 30 described above, the cost of the shield case 38 and the cover plates 39a, 39b is high, and the entire power supply circuit is covered by the shield case 38 and the cover plates 39a, 39b. Case 38 and lid plate 39
Despite the large number of ventilation holes provided in a and 39b, heat builds up inside the shield case due to the heat generated by the power transistor 34, etc., and the input lead wire 36 and output lead wire 37 are
Heavy insulated lead wires had to be used, increasing costs. Another drawback was that it was difficult to remove the circuit board during service.

Therefore, the present applicant has previously filed Utility Application No. 118363/1983 in order to improve the above invention.

This shield device is shown in FIG.

This shield device 40 includes PRT41, PIT42,
Input connector lead 43, output connector lead 4
4. A circuit board 46 on which a rectifier diode 45 etc. are installed and forms a power supply circuit, and a power transistor 4
The upper shield case 48a and the lower shield case 4 are installed to serve as a heat sink.
8b.

The upper shield case 48a is provided with a locking piece 49a, and the locking piece 49a is inserted into a slit 49b provided on the circuit board 46, and the power transistor is inserted into a predetermined position on the side surface of the shield case 48a. 47 will be installed. and,
A locking piece 50a provided on the lower shield case 48b is inserted and projected into a slit 50b provided on the circuit board 46, the power transistor 47 is sandwiched therebetween, and the assembly is completed by fixing with screws 51.

The assembled shield device 40 is screwed to the chassis through screw holes 52 provided at the four corners of the circuit board 46.

By the way, when this shield device 40 is assembled, there are openings in the upper shield case 48a and the lower shield case 48b, so the leakage magnetic flux of the PRT 41 and PIT 42 jumps out in the direction of the opening. It was causing negative effects such as loading the installed electronic equipment, interfering with the sound of speakers, and interfering with the power supply of color cathode ray tube television screens.

Additionally, since CRT landing interference occurs, it was necessary to consider the installation location of the shield device.

Since the power transistor 47 is installed in the upper shield case 48a,
The primary side is at ground potential, and the upper shield case 48 is connected to the AC line during service.
Because there is a risk of electric shock if you touch a, it was necessary to put up a label such as ``Caution for electric shock.''

Furthermore, as PITs have become larger due to today's increased load power, the method of fixing the circuit board 46 to the chassis with screws through the screw holes 52 provided at the four corners of the circuit board 46 has lower vibration and drop strength. I felt anxious.

The present invention was developed in view of these circumstances, and has a simple structure that completely shields leakage magnetic flux from PRTs, PITs, etc., and efficiently dissipates heat generated by switching transistors, etc., thereby preventing electric shocks and the like during service. The purpose of the present invention is to provide a shielding device that allows a circuit board to be easily taken out without worrying about it, is low in cost, and has strong vibration and drop strength.

[Means to solve the problem]

The shielding device according to the present invention includes a pair of heat sinks that are erected on a circuit board and shield the power supply circuit section disposed on the circuit board between them, A pair of shield plates each having a U-shaped cross section are arranged to sandwich the power supply circuit section, and the power supply circuit section can be The above problem is solved by using this shield device in a shield device that is characterized by surrounding from all directions.

[Effect]

In the shielding device according to the present invention, by surrounding the power supply circuit section in all directions with a heat sink and a pair of shield plates, leakage magnetic flux from magnetic generation components such as PRT and PIT in the power supply circuit section is completely shielded. can.

Further, since the heat sink is arranged in the opening of the pair of shield plates combined, the heat radiated through the heat sink is no longer trapped in the shield plate.

〔Example〕

Embodiments of the shield device according to the present invention will be described below with reference to the drawings.

FIG. 1 is an exploded perspective view showing a shield device according to an embodiment of the present invention.

In the shield device 1 shown in FIG. 1, circuit components such as an input connector plug 3, an output connector plug 4, a PRT 5, and a PIT 6 are installed on a circuit board 2.
For example, a magnetic flux control type switching power supply circuit as disclosed in Japanese Patent Application Laid-Open No. 62-64266 is formed.

PIT6 of this magnetic flux control type switching power supply circuit
operates by leakage inductance, and because the primary winding and the secondary winding are wound across the bobbin with an insulating distance between them, a large amount of leakage magnetic flux is generated. For this reason, the above PRT5, PIT6
Shielding magnetic flux leakage becomes important.

Therefore, in the shield device 1 according to the present invention, a pair of U-shaped iron heat sinks 7, which are erected on the circuit board 2 and shield the power supply circuit section arranged on the circuit board 2, are provided. 8 are erected.

The heat sinks 7 and 8 each have extensions 7b and 7c on the main body 7a and extensions 8b and 8c on the main body 8a. When the heat sinks 7 and 8 are installed on the circuit board, they surround at least the magnetic generating components such as the PRT 5 and the PIT 6.
The legs 7b and 8b, and 7c and 8c are disposed opposite each other with a predetermined gap g therebetween.

At predetermined positions on the outer peripheral surfaces of the heat sinks 7 and 8,
6 primary side switching transistors 9 and 2
Two next-side rectifier diodes 10 are installed at a constant distance from each other.

Here, the two heat sinks are usually connected to the switching transistor 9 and the rectifier diode 10.
The above-mentioned gap g is provided in order to insulate between the heat sinks 7 and 8, taking into consideration that each of the heat sinks 7 and 8 has a ground potential.

Further, in order to radiate the heat generated by the switching transistor 9 and the rectifier diode 10, the heat radiating plates 7 and 8 are provided with ventilation holes 11 to enhance the heat radiating effect.
is provided.

The heat sinks 7 and 8 also have the effect of shielding leakage magnetic flux from the PRT 5 and PIT 6, and prevent leakage magnetic flux in the X direction shown by the arrow in FIG. 1, which is one direction on the plane of the circuit board 2, from the main body 7a. , 8a, it is completely shielded. Then, the circuit board 2
Regarding the leakage in the Y direction shown by the arrow in FIG. 1, which is one direction on the plane of the
It is shielded by c and 8c. However, leakage magnetic flux remains at the location where the air gap g is provided.

On the side of the gap between the heat sinks 7 and 8 of the circuit board 2, four slits 12 are provided on each side. This slit 12 is provided with four locking pieces 13 each on the left and right side surfaces of a pair of iron shield plates 13 and 14 each having a U-shaped cross section.
a, 14a are inserted with the circuit board 2 in between.

Then, the shield case 1
By fixing 3 and 14 with screws, the circuit board 2 and the shield plates 13 and 14 can be completely fixed.

Note that the input connector plug 3 and the output connector plug 4 are provided at the ends of the circuit board, respectively, so that it is easy to connect the input side lead wire and the output side lead wire to the respective plugs 3 and 4. There is.

FIG. 2 shows the shield device assembled as described above.

As shown in FIG. 2, the heat sinks 7 and 8 are arranged inside the shield plates 13 and 14, and the shield plates 13 and 14 are provided with ventilation holes 15 and 16, respectively. In addition, the shield plate 1 is placed in the direction in which the switching transistor 9 and the rectifier diode 10 are installed.
Since the shield plates 13 and 14 are arranged with openings, the heat generated by the switching transistor 9 and the rectifier diode 10 will not be trapped inside the shield plates 13 and 14.

Furthermore, by the shield plates 13 and 14,
The heat sink 7 is in the Y direction indicated by the arrow in FIG. 1, which is one direction on the plane of the circuit board 2 of PRT5, PIT6.
The magnetic flux leaking from the gap g between b and 8b and between 7c and 8c and the first direction in one direction on the plane of the circuit board 2
Since leakage magnetic flux in the Z direction, which is a direction orthogonal to the X direction and Y direction shown by arrows in the figure, can be shielded, magnetic shielding in all directions of the PRT 5 and PIT 6 can be achieved.

It is supported by the chassis 24 by a cut-and-raised portion 13c provided on the upper shield plate 13, and screwed to the chassis 24 through a screw hole 13d provided in the cut-and-raised portion 13c.

As is clear from the above explanation, the shield device 1 according to the present invention can completely shield leakage magnetic flux from the PRT 5, PIT 6, etc., so there is no problem when installing it anywhere in the electronic device, and at the same time, it can be installed anywhere in the electronic device. switching transistor 9 and rectifier diode 1
Since it is possible to dissipate even heat generated by zero or the like, the heat dissipation plate and the shield plate can be made of inexpensive iron, and costs can be reduced.

Furthermore, since the structure is simple, it is easy to take out the circuit board 2, and service is also improved.

The switching transistor 46 is not directly attached to the shield case 47a as in the shield device 40 proposed earlier by the inventor of the present invention, but instead of the shield plate 13, the above-mentioned heat sinks 7 and 8 are provided separately. Since the switching transistor 9 and rectifier diode 10 are installed, there is no problem with grounding and there is no fear of electric shock.

Furthermore, since the shield plate is screwed to the chassis rather than the circuit board screwed to the chassis as in the past, the vibration and fall strength can be increased, making it possible to handle even larger PITs.

[Effect of idea]

As is clear from the above explanation, the shield device according to the present invention can completely shield leakage magnetic flux from PRT, PIT, etc. by using a shield plate and a heat sink provided separately from the shield plate, and also can completely shield magnetic flux leakage from PRT, PIT, etc. Since the heat generated by the switching transistors and rectifier diodes placed in the electronic device can be dissipated without being trapped, the device can be made of inexpensive steel, reducing costs and allowing it to be installed anywhere in the electronic device. Furthermore, since it can be realized with a simple structure, it has become easier to take out the circuit board.

Furthermore, as in this embodiment, the heat sink is disposed inside the shield plate, so there is no fear of electric shock or the like even if the heat sink is touched while the AC line is connected during service.

By attaching the shield plate directly to the chassis, it is possible to provide a shield device with strong vibration and drop strength.

[Brief explanation of the drawing]

Fig. 1 is an exploded perspective view of a shielding device as an embodiment of the present invention, Fig. 2 is an assembled perspective view of a shielding device as an embodiment of the present invention, and Fig. 3 is a conventional fully enclosed shielding device. Exploded perspective view, 4th
The figure is an exploded perspective view of the shield device previously proposed by the inventor of the present invention. 1, 30, 40...shield device, 5, 32,
41...PRT, 6, 31, 42...PIT, 7,
8... Heat sink, 13, 14... Shield plate.

Claims (1)

[Scope of Claim for Utility Model Registration] A pair of heat sinks installed upright on a circuit board to sandwich and shield a power supply circuit section disposed on the circuit board; A pair of shield plates each having a U-shaped cross section are arranged to sandwich the power supply circuit section, and by placing the heat dissipation plate in the opening of the pair of shield plates combined, the power supply circuit section can be A power supply circuit shielding device that is characterized by enclosing it from all directions.